System and method for determining angle of arrival for communications

ABSTRACT

A system and method for determining an Angle of Arrival (AOA) for frequency modulated communications. The system may include first and second antennas spaced apart from each other by a distance, and configured to receive wireless communications in the form of a modulated signal. The system may determine a phase difference between the received signals based on one or more samples of a dedicated portion of the received signals, where one or more aspects of the dedicated portion is variable.

FIELD OF THE INVENTION

The present application relates to determining an angle of arrival withrespect to a wireless signal, and more particularly toward determiningan angle of arrival (AOA) for communications.

BACKGROUND

AOA can be computed by comparing the phase of RF signals output from twoantennas. Conventional techniques for comparing the RF signals rely inphase locked receivers to compare phase or a single signal commutatedreceiver to compare the phase during subsequent intervals during asingle dedicated section of a message packet communicated in the RFsignals.

One conventional type of AOA computation device uses a single dedicatedsection of the payload of a message packet with a duration in the rangeof a few microseconds. There are several downsides to this approach.First, the single dedicated section may not be standardized for thecommunication protocol used to generate the message packet, leaving somedevices incapable of understanding the data within the message packetdue to the single dedicated section. Second, the single dedicatedsection may reduce the time allowed for data transmission (e.g., ittakes up a portion of the payload). To avoid significant reduction, thesingle dedicated packet in conventional systems is short in duration,leaving only a brief window for AOA to be determined and therefore theAOA determination can be prone to error. Third, as the single dedicatedsection becomes shorter, the processing bandwidth becomes larger and sonoise-induced errors are likely to increase.

For at least these reasons, conventional phase-based AOA systems areoften incompatible with devices that implement a particularcommunication protocol that has been adapted for AOA determinations.Additionally, these conventional systems are often unable to achieve aworkable compromise between the size of the single dedicated section andthe size of the payload or data in accordance with the communicationprotocol.

SUMMARY

A system and method are provided for determining an AOA based on RFsignals output from at least two antennas. The RF signals may berepresentative of an electromagnetic wave received by the at least twoantennas. The AOA determination may be based on a phase measurement ofthe RF signals for an arbitrary length of a standard communicationspacket received in accordance with a communications protocol. The phasemeasurement may be determined without compromising the data packet witha dedicated section and for an arbitrary period of time to enhance theaccuracy of the phase measurement. This way, the phase measurement canbe obtained with respect to any device capable of communicating inaccordance with the communications protocol.

In one embodiment, the system may be based on a single, commutatedreceiver that compares received phase on subsequent sections of amessage packet transmitted in accordance with the communicationsprotocol.

In one embodiment, the system may use multiple phase-locked receivers tocompare the received phase from both receivers.

In one embodiment, a system is provided for determining an angle ofarrival for frequency modulated communications. The system may include afirst antenna, a second antenna, and a controller. The first antenna maybe capable of wirelessly receiving the frequency modulatedcommunications to generate a first frequency modulated output. Thesecond antenna may be separated by a distance from the first antenna,and capable of wirelessly receiving the frequency modulatedcommunications to generate a second frequency modulated output. Thefirst frequency modulated output and the second frequency modulatedoutput are indicative of the frequency modulated communications arrivingat the first and second antennas at different times.

The controller may be configured to determine a phase difference betweenthe first and second frequency modulated outputs received by the firstand second antennas, where the phase difference is determined based onunmodulated forms determined from the first and second frequencymodulated outputs, and where the phase difference is determinedirrespective of frequency modulations in the first and second frequencymodulated outputs.

In one embodiment, a method is provided for determining an angle ofarrival for frequency modulated communications. The method may includegenerating a first frequency modulated output based on wireless receiptof the frequency modulated communications in a first antenna, andgenerating a second frequency modulated output based on wireless receiptof the frequency modulated communications in a second antenna, whereinthe second antenna is separated by a distance from the first antenna.The method may also include producing first and second unmodulated formsof the first and second frequency modulated outputs. A phase differencemay be determined based on the first and second unmodulated forms suchthat the phase difference is determined irrespective of frequencymodulations in the first and second frequency modulated outputs.

In one embodiment, a system is provided for determining an angle ofarrival for a wireless communication signal. The system may include afirst antenna capable of wirelessly receiving a first arbitrary lengthof the wireless communication signal to facilitate generation of a firstfrequency modulated segment. The system may include a second antennaseparated by a distance from said first antenna, and capable ofwirelessly receiving a second arbitrary length of the wirelesscommunication signal to facilitate generation of a second frequencymodulated segment. The first frequency modulated segment and the secondfrequency modulated segment may arrive at the first and second antennasat different times, and the first and second modulated segments includefrequency modulations representative of data.

The system may include a controller configured to determine a phasedifference between the first and second frequency modulated segmentsreceived by the first and second antennas, where the phase difference isdetermined based on unmodulated forms of the first and second frequencymodulated segments and irrespective of the frequency modulationsrepresentative of data.

In one embodiment, a system is provided for determining an angle ofarrival for modulated communications. The system may include a firstantenna, a second antenna, and a controller. The first antenna may becapable of wirelessly receiving the modulated communications to generatea first modulated output. The second antenna may be separated by adistance from the first antenna, and may be capable of wirelesslyreceiving the modulated communications to generate a second modulatedoutput. The first modulated output and the second modulated output maybe indicative of the modulated communications arriving at the first andsecond antennas at different times, and where the modulatedcommunications include a plurality of dedicated portions during whichone or more characteristics of the modulated communications arepre-determined.

The controller may be configured to determine a phase difference betweenthe first and second modulated outputs received by the first and secondantennas, wherein the phase difference is determined based on one ormore samples of the first and second modulated outputs during periodscorresponding to the plurality of dedicated portions.

In one embodiment, a method is provided for determining an angle ofarrival for modulated communications. The method may include generatinga first modulated output based on wireless receipt of the modulatedcommunications in a first antenna, and generating a second modulatedoutput based on wireless receipt of the modulated communications in asecond antenna. The second antenna may be separated by a distance fromthe first antenna. The method may include sampling the first and secondmodulated outputs corresponding to at least a portion of a plurality ofdedicated sections of the modulated communications, and determining aphase difference based on samples of the first and second modulatedoutputs.

In one embodiment, a transmission device is provided for facilitatingdetermining an angle of arrival for a wireless communication signaltransmitted from the transmission device. The transmission device mayinclude an antenna array configured to transmit the wirelesscommunication signal via an electromagnetic waveform provided to remotedevice. The antenna array may include one or more antennas. Thetransmission device may include a communication interface including atransmitter configured to transmit a plurality of message packets in thewireless communication signal. The plurality of message packets mayinclude a dedicated portion during which one or more characteristics ofthe wireless communication signal are pre-determined, and where presenceof the dedicated portion in the wireless communication signalfacilitates determining an angle of arrival for the wirelesscommunication signal relative to the remote device. The one or morecharacteristics may be pre-determined prior to transmission of thededicated portion. As an example, the communication interface maydetermine the one or more characteristics in conjunction withtransmitting a message packet that includes the dedicated portion. Theone or more characteristics may be communicated in the data packet priorto transmission of the dedicated portion.

The communication interface may be configured to dynamically vary theone or more characteristics of the dedicated portion such that the oneor more characteristics for a first dedicated portion of a first messagepacket are different form the one or more characteristics for a seconddedicated portion of a second message packet. The communicationinterface may be configured to communicate dedicated portion informationpertaining to the one or more characteristics to the remote device priorto transmission of the dedicated portion.

Before the embodiments of the invention are explained in detail, it isto be understood that the invention is not limited to the details ofoperation or to the details of construction and the arrangement of thecomponents set forth in the following description or illustrated in thedrawings. The invention may be implemented in various other embodimentsand of being practiced or being carried out in alternative ways notexpressly disclosed herein. Also, it is to be understood that thephraseology and terminology used herein are for the purpose ofdescription and should not be regarded as limiting. The use of“including” and “comprising” and variations thereof is meant toencompass the items listed thereafter and equivalents thereof as well asadditional items and equivalents thereof. Further, enumeration may beused in the description of various embodiments. Unless otherwiseexpressly stated, the use of enumeration should not be construed aslimiting the invention to any specific order or number of components.Nor should the use of enumeration be construed as excluding from thescope of the invention any additional steps or components that might becombined with or into the enumerated steps or components.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a representative view of two antennas configured to receive anelectromagnetic wave and depicts an angle of arrival of the waverelative to the two antennas.

FIG. 2 is another representative view of two antennas configured toreceive an electromagnetic wave and depicts an angle of arrival of thewave relative to the two antennas.

FIG. 3 is a system in accordance with one embodiment.

FIG. 4 is a representative view of a device in accordance with oneembodiment.

FIG. 5 is a representative view of RF communications with encoded datain accordance with one embodiment.

FIG. 6 depicts first and second antennas coupled to a phase detector inaccordance with one embodiment.

FIG. 7A shows a message packet in accordance with one embodiment.

FIG. 7B shows a data stream within the message packet that correspondsto a dedicated portion for determining a phase difference in accordancewith one embodiment.

FIG. 7C shows data values for the dedicated portion in accordance withone embodiment.

FIG. 7D shows a control signal or switch input for switching betweenfirst and second antennas in accordance with one embodiment.

FIG. 7E shows a control signal or switch input for switching betweenfirst and second antennas in accordance with one embodiment.

FIG. 8 depicts first and second antennas coupled to a phase detector inaccordance with one embodiment.

FIG. 9 depicts first and second antennas coupled to a phase detector inaccordance with one embodiment.

FIG. 10 depicts first and second antennas coupled to a phase detector inaccordance with one embodiment.

FIG. 11 shows a MODEM in accordance with one embodiment.

FIG. 12 shows a digitally controlled oscillator in accordance with oneembodiment.

FIG. 13 shows a digitally controlled oscillator in accordance with oneembodiment.

DETAILED DESCRIPTION

A system and method for determining an Angle of Arrival (AOA) forfrequency modulated communications are provided in connection with oneor more embodiments of the present disclosure. The system may includefirst and second antennas spaced apart from each other by a distance.Both the first and second antennas may be configured to receive wirelesscommunications in the form of a frequency modulated signal. The systemmay determine a phase difference between the received signalsirrespective of the modulations in the signal, thereby facilitatingdetermining an AOA. It is noted that AOA may not be determined solely inaccordance with one or more embodiments described herein. AOAdeterminations may be supplemented in accordance with one or more othertechniques, including AOA determinations based on amplitude or a hybridof amplitude and phase.

First and second antennas 102-A1, 102-A2 are shown in the illustratedembodiments of FIGS. 1 and 2 in accordance with one embodiment of thepresent disclosure. The first and second antennas 102-A1, 102-A2 may beseparated by a distance d and configured to receive electromagneticwaves propagating through space from a source. In one embodiment, suchas the one depicted in the illustrated embodiment of FIG. 3, the sourceof the electromagnetic waves may be a portable device 20, and the firstand second antennas 102-A1, 102-A2 may form an antenna array 30 disposedon an object 10. The present disclosure is not limited to an antennaarray 30 having first and second antennas 102—the antenna array 30 mayinclude one or more antennas 102, including three or more antennas 102provided in a spaced-apart configuration. Optionally, the beam of one ormore antennas 102 of a plurality in the antenna array 30 may bedifferent from another beam of at least one other antenna 102 of theplurality. Differences in the beam may include directionality (e.g.,omnidirectional or directional), and gain, or a combination thereof.

In the illustrated embodiment of FIGS. 1 and 2, the first and secondantennas 102-A1, 102-A2 are separated by a distance d, and configured toreceive the plane wave 101 having a frequency (e.g., a carrierfrequency) corresponding to a wavelength λ. Each antenna 102-A1, 102-A2may output a waveform signal corresponding to components of the planewave 101 detected by the antenna 102-A1, 102-A2. For purposes ofdiscussion, the distance d separating the first and second antennas102-A1, 102-A2 is half the wavelength λ of the frequency of the planewave 101. This way, the AOA of the plane wave 101 relative to the firstand second antennas 102-A1, 102-A2 is half the phase difference of thewaveform signal output from the first and second antennas 102-A1,102-A2. This phase difference may be output as a phase difference signal104, which, in one embodiment, has a voltage corresponding to a value ofthe phase difference (e.g., 2.5V=>0°, 5V=>°90, 0V=>−90°).

In one example, if the source of the plane wave 101 impinging the firstand second antennas 102-A1, 102-A2 is positioned at 900 to the first andsecond antennas 102-A1, 102-A2, the waveform signal output from thesecond antenna 102-A2 leads the waveform signal output from the firstantenna 102-A1 by 180°. By determining the phase difference between thewave form signals output from the first and second antennas 102-A1,102-A2, the AOA can be identified. In this example, by determining thephase difference is 180°, and with the distance d being half thewavelength λ, the AOA can be determined as 90°. As another example, ifthe phase difference of the waveform signals output from the first andsecond antennas 102-A1, 102-A2 is 0°, the AOA can be determined as 0°.And if the phase difference of the waveform signals output from thefirst and second antennas 102-A1, 102-A2 is −180°, the AOA can bedetermined as −90°.

Based on these examples it can be seen that, with the distance d beinghalf the wavelength λ, the AOA is half the phase difference determinedwith respect to the plane wave 101 detected by the first and secondantennas 102-A1, 102-A2. The distance d may vary from application toapplication and need not be half the wavelength λ. Rather, this distanced is provided to facilitate understanding with respect to FIG. 2, and todemonstrate that the AOA may be determined as a function of the phasedifference determined with respect to the plane wave 101 detected by thefirst and second antennas 102-A1, 102-A2.

For purposes of disclosure, the example in FIG. 2 is described inconjunction with determining AOA for receipt of a plane wave 101impinging two antennas 102. A waveform signal output from additionalantennas may be compared against the waveform signals noted above fordetermining AOA with further confidence or AOA in three-dimensions, orboth. For instance, with three antennas 102 separated from each othersuch that each antenna 102 is separated from an adjacent antenna 102 bydistance d (forming an equilateral triangle), the AOA may be determinedin three dimensional space rather than relative to a projection of thesource location onto a plane in accordance with one embodiment.

I. System Overview

A system in accordance with one embodiment is shown in the illustratedembodiment of FIG. 3 and generally designated 100. The system 100 mayinclude one or more system components as outlined herein. A systemcomponent may be a user or an electronic system component, which may bethe portable device 20, a sensor 40, and an object component 50. Theobject component 50, as discussed herein, may be configured to operateas any one or more of these devices. In this sense, in one embodiment,there may be several aspects or features common among the portabledevice 20, the sensor 40, and the object component 50. In other words,the features described in connection with the object component 50depicted in FIG. 4 may be incorporated into the portable device 20 orthe sensor 40, or both. In one embodiment, the object component 50 mayform an equipment component disposed on an object 10, such as a vehicleor a building. The object component 50 may be communicatively coupled toone or more systems of the object 10 to control operation of the object10, to transmit information to the one or more systems of the object 10,or to receive information from the one or more systems of the object 10,or a combination thereof.

The object component 50 may include one or more processors 51 thatexecute one or more applications 57 (software and/or includes firmware),one or more memory units 52 (e.g., RAM and/or ROM), and one or morecommunication interfaces 53, amongst other electronic hardware. Theobject component 50 may or may not have an operating system 56 thatcontrols access to lower-level devices/electronics via a communicationinterface 53. The object component 50 may or may not have hardware-basedcryptography units 55—in their absence, cryptographic functions may beperformed in software. The object component 50 may or may not have (orhave access to) secure memory units 54 (e.g., a secure element or ahardware security module (HSM)). Optional components and communicationpaths are shown in phantom lines in the illustrated embodiment.

The system 100 in the illustrated embodiment of FIG. 3 is not dependentupon the presence of a secure memory unit 54 in any component. In theoptional absence of a secure memory unit 54, data that may otherwise bestored in the secure memory unit 54 (e.g., private and/or secret keys)may be encrypted at rest (when possible). Both software-based andhardware-based mitigations may be utilized to substantially preventaccess to such data, as well as substantially prevent or detect, orboth, overall system component compromise. Examples of such mitigationfeatures include implementing physical obstructions or shields,disabling JTAG and other ports, hardening software interfaces toeliminate attack vectors, using trusted execution environments (e.g.,hardware or software, or both), and detecting operating system rootaccess or compromise.

For purposes of disclosure, being secure is generally considered beingconfidential (encrypted), authenticated, and integrity-verified. Itshould be understood, however, that the present disclosure is not solimited, and that the term “secure” may be a subset of these aspects ormay include additional aspects related to data security.

The communication interface 53 may be any type of communication link,including any of the types of communication links describe herein,including wired or wireless. The communication interface 53 mayfacilitate external or internal, or both, communications. For instance,the communication interface 53 may be coupled to or incorporate theantenna array 30.

As another example, the communication interface 53 may provide awireless communication link with another object component 50 in the formof the portable device 20, such as wireless communications according tothe WiFi standard. In another example, the communication interface 53may be configured to communicate with an equipment component of avehicle (e.g., a vehicle component) via a wired link such as a CAN-basedwired network that facilitates communication between a plurality ofdevices. The communication interface 53 in one embodiment may include adisplay and/or input interface for communicating information to and/orreceiving information from a user 60.

In one embodiment, shown in FIG. 4, the object component 50 may beconfigured to communicate with one or more auxiliary devices other thananother object component 50 or a user. The auxiliary device may beconfigured differently from the object component 50—e.g., the auxiliarydevice may not include a processor 51, and instead, may include at leastone direct connection and/or a communication interface for transmissionor receipt, or both, of information with the object component 50. Forinstance, the auxiliary device may be a solenoid that accepts an inputfrom the object component 50, or the auxiliary device may be a sensor(e.g., a proximity sensor) that provides analog and/or digital feedbackto the electronic system component 200.

The system 100 in the illustrated embodiment may be configured todetermine location information in real-time with respect to the portabledevice 20. In the illustrated embodiment of FIG. 3, the user 60 maycarry the portable device 20 (e.g., a smartphone). The system 100 mayfacilitate locating the portable device 20 with respect to the object 10(e.g., a vehicle) in real-time with sufficient precision to determinewhether the user is located at a position at which access to the objector permission for an object command should be granted.

For instance, in an embodiment where the object 10 is a vehicle, thesystem 100 may facilitate determining whether the portable device 20 isoutside the vehicle but in close proximity, such as within 5 feet, 3feet, or 2 feet or less, to the driver-side door. This determination mayform the basis for identifying whether the system 100 should unlock thevehicle. On the other hand, if the system 100 determines the portabledevice 20 is outside the vehicle and not in close proximity to thedriver-side door (e.g., outside the range of 2 feet, 3 feet, or 5 feet),the system 100 may determine to lock the driver-side door. As anotherexample, if the system 100 determines the portable device 20 is in closeproximity to the driver-side seat but not in proximity to the passengerseat or the rear seat, the system 100 may determine to enablemobilization of the vehicle. Conversely, if the portable device 20 isdetermined to be outside close proximity to the driver-side seat, thesystem 100 may determine to immobilize or maintain immobilization of thevehicle.

The object 10 may include multiple object components 50 or variantthereof, such as a sensor 40 coupled to an antenna array 30 inaccordance with one or more embodiments described herein. The sensor 40may be configured to determine an angle of arrival with respect tocommunications with the portable device 20, based at least in part on aphase difference determined with respect to communications received bytwo or more of the antennas 102 of the antenna array 30.

Micro-location of the portable device 20 may be determined in a varietyof ways, such as using information obtained from a global positioningsystem, one or more signal characteristics of communications from theportable device 20, and one or more sensors (e.g., a proximity sensor, alimit switch, or a visual sensor), or a combination thereof. An exampleof microlocation techniques for which the system 100 can be configuredare disclosed in U.S. Nonprovisional patent application Ser. No.15/488,136 to Raymond Michael Stitt et al., entitled SYSTEM AND METHODFOR ESTABLISHING REAL-TIME LOCATION, filed Apr. 14, 2017—the disclosureof which is hereby incorporated by reference in its entirety.

In one embodiment, in the illustrated embodiment of FIG. 3, the objectcomponent 50 (e.g., a system control module (SCM)) and a plurality ofsensors 40 (coupled to an antenna array 30) may be disposed on or in afixed position relative to the object 10. Example use cases of theobject 10 include the vehicle identified in the prior example, or abuilding for which access is controlled by the object component 50. Thesensors 40 in the illustrated embodiment may be incorporated or becoupled to one or more antennas 102 as described herein. The arrangementor position of the sensors 40 may be in accordance with one or moreembodiments described herein. Signal processing of the object component50 may be in accordance with one or more embodiments described herein.

The portable device 20 may communicate wirelessly with the objectcomponent 50 via a communication link. The plurality of sensors 40 maybe configured to sniff the communications between the portable device 20and the object component 50 to determine one or more signalcharacteristics of the communications, such as signal strength or angleof arrival, or both. The determined signal characteristics may becommunicated or analyzed and then communicated to the object component50 via a communication link separate from the communication link betweenthe portable devices 20 and the object component 50. Additionally, oralternatively, the portable device 20 may establish a directcommunication link with one or more of the sensors 40, and the one ormore signal characteristics may be determined based on this directcommunication link.

As an example, as shown in the illustrated embodiment, the angle ofarrival with respect to communications transmitted to antenna arrays30A, 30B may vary depending on the location of the portable device 20relative to the antenna arrays 30A, 30B. At the position shown in theillustrated embodiment of FIG. 3, the portable device 20 may transmitcommunications that arrive at the antenna array 30A at a first angle θ₁and arrive at the antenna array 30B at a second angle θ₂, which is moreacute or smaller than the first angle θ₁. Based on at least these twoangles of arrival, a position of the portable device 20 may bedetermined or an accuracy of a position of the portable device 20determined in conjunction with one or more other sensed characteristicsmay be increased.

As described herein, one or more signal characteristics, such as signalstrength and angle of arrival, may be analyzed to determine locationinformation about the portable device 20 relative to the object 10, anaspect of the object 10, or the object component 50, or a combinationthereof. For instance, time difference of arrival or the angle ofarrival, or both, among the sensors 40 and the object component 50 maybe processed to determine a relative position of the portable device 20.The positions of the one or more antenna arrays 30 relative to theobject component 50 may be known so that the relative position of theportable device 20 can be translated to an absolute position withrespect to the antenna arrays 30 and the object component 50.

Additional or alternative examples of signal characteristics may beobtained to facilitate determining position according to one or morealgorithms, including a distance function, trilateration function, atriangulation function, a multilateration function, a fingerprintingfunction, a differential function, a time of flight function, a time ofarrival function, a time difference of arrival function, an angle ofdeparture function, a geometric function, etc., or any combinationthereof.

II. Phase Detector

A phase detection component 70 in accordance with one or moreembodiments may be incorporated into the system 100 to determine a phasedifference between waveform signals output from two or more antennas102. The phase detection component 70 may be incorporated into thecommunication interface 53 of the sensor 40 in accordance with oneembodiment. The phase detection component 70 in one embodiment may forma receiver capable of demodulating communications received via thewaveform signals output from the two or more antennas 102.

The phase detection component 70 may be configured to generate a phasedifference output, such as the phase difference signal 104 described inconjunction with the illustrated embodiments of FIGS. 1 and 2. The phasedifference output may be any type of output indicative of a phasedifference, including, for example, an analog signal with a voltagerepresentative of the phase difference, a PWM signal with a duty cyclerepresentative of the phase difference, a serial set of bitsrepresentative of the phase difference that can be communicated toanother component, and a memory register in which the phase differenceis stored, or any combination thereof.

Based on the phase difference of the waveform signals output from firstand second antennas 102, the system 100 may determine an angle ofarrival with respect to the electromagnetic wave that generated thewaveform signals output from the first and second antennas 102. In theillustrated embodiment, the wave is generated by the portable device 20,but it should be understood that the wave may be generated by anycomponent of the system 100, including from a sensor 40.

An example of a function for determining an angle of arrival based on aphase difference between waveform output signals from first and secondantennas 102 is described in conjunction with the illustratedembodiments of FIGS. 1 and 2. The angle of arrival may be determined inthe object component 50, or the sensor 40, or any component of thesystem 100, or any combination thereof. In one embodiment, the angle ofarrival may be determined with respect to multiple pairs of antennas 102(e.g., a first antenna 102 and a second antenna 102, the second antenna102 and a third antenna 102, and the first antenna 102 and the thirdantenna 102). Based on the angle of arrival for one or more pairs ofantennas 102, information about the position of the portable device 20may be determined.

The electromagnetic wave generated by the portable device 20, or anothercomponent of the system 100, may vary depending on the application andwhether communications (e.g., data bits) are being transmitted. In oneembodiment, the electromagnetic wave may include a carrier wave having afrequency FC. The electromagnetic wave may remain substantially constantat the frequency FC or another frequency with no communications and nomodulations. For instance, the electromagnetic wave may be substantiallyconstant for its entire duration or may be substantially constant for aperiod of time.

In one embodiment, the electromagnetic wave may be modulated to transmitcommunications from a first device to a second device. Thecommunications may include data a) generated and transmitted from thefirst device and b) received and processed by the second device. Themodulation scheme utilized for transmission of communications may varyfrom application to application. Example modulation schemes includefrequency shift keying (FSK), amplitude shift keying (ASK), minimumshift keying (MSK), and Gaussian minimum shift keying (GMSK).

A representation of modulations on an electromagnetic wave in accordancewith one embodiment is shown in FIG. 5. The diagram in the illustratedembodiment depicts frequency versus time for a GMSK frequency modulatedwaveform with symbols (e.g., data bits) represented by first and secondfrequencies 204, 206 respectively at f1, f2, which may be centered abouta center frequency f0. In other words, the electromagnetic waveform 201shown in FIG. 5 is a 2-level (or two symbol) GMSK Frequency Modulation(FM) waveform.

In the illustrated embodiment, changing from the first frequency 204 tothe second frequency 206 from the second frequency 206 to the firstfrequency 204 may facilitate transmission of symbols or communicationsvia the electromagnetic wave. An example of this mode of communicationincludes a center frequency at 2.402 MHz and the first and secondfrequencies 204, 206 respectively at +180 kHz and −180 kHz relative tothe center frequency.

It is noted that GMSK has characteristics that make it useful forphase-based AOA. For instance, when transmitting a sequence of the samesymbol, the frequency may remain substantially constant or stable andnot change. Additionally, when changing from one symbol to another, thephase in GMSK may be continuous.

In one embodiment, as discussed herein, the phase difference output maybe determined with respect to a portion 203 of the electromagneticwaveform that includes modulations. Because changes due to modulationsmay occur at different points in time of the electromagnetic wave, andbecause the first and second antennas 102 of a phase detector in oneembodiment may be separated by a distance d, the phase detector may bedetermining a phase difference between a first waveform output at thefirst frequency 204 and a second waveform output at the second frequency206. For instance, at or near the transition from the first frequency204 to the second frequency 206, the first antenna 102 (if closer to theelectromagnetic waveform source) may output a waveform signal thatcorresponds to the second frequency 206 while at the same time thesecond antenna 102 (if farther away from the electromagnetic waveformsource) may output a waveform signal that still corresponds to the firstfrequency 204.

One embodiment according to the present disclosure may remove themodulations from the waveform output signals generated by the first andsecond antennas 102, thereby providing a comparison based on unmodulatedforms of the waveform output signals. As an example, the waveform outputsignals from the first antenna 102 and the second antenna 102 may beprocessed to yield unmodulated waveform output signals having a commonfrequency (e.g., the carrier frequency) without modulations. The phasesof the two unmodulated waveform output signals can be compared againsteach other to yield a phase difference output in accordance with oneembodiment. The modulations may be dynamically removed from the waveformoutput signals—that is, instead of knowing beforehand what themodulations will be in order to remove them from the waveform outputsignals, the modulations may be determined from the waveform outputsignal and removed therefrom in a dynamic manner.

In one embodiment, by removing the modulations from the waveform outputsignals, a phase difference can be determined for the waveform outputsignals generated from the first and second antennas 102 for periods oftime substantially longer than a message packet in accordance with acommunication protocol, a portion of such a message packet, or aduration between message packets, or any combination thereof. Forpurposes of disclosure, the message frame may be an Ethernet packet or apacket similar to the one depicted in the illustrated embodiment of FIG.7. In other words, it is not necessary in one embodiment to wait untilthe waveform output signals are known to share a common frequency inorder to determine a phase difference output for the two signals. Thephase difference output can be determined with respect to the waveformoutput signals from first and second antennas 102 irrespective of anyfrequency modulations in the electromagnetic wave that provides thebasis for the waveform output signals.

In an alternative embodiment, the phase difference output may bedetermined based on a comparison of the waveform output signals for adedicated or assigned portion 202 of the electromagnetic waveform. Thededicated portion 202 of the electromagnetic waveform may provide aperiod during which one or more aspects of the electromagnetic waveform201 are known or pre-determined, and therefore facilitate determiningthe phase difference. Pre-determination of the dedicated portion 202 maybe include dynamically determining one or more aspects of the dedicatedportion 202 (e.g., time location within a message packet, a duration, ora modulation content, or a combination thereof) before transmission ofthe dedicated portion 202. In one embodiment, these one or more aspectsmay be communicated to a receiver in the same message packet as thededicated portion 202 but prior to transmission of the dedicated portion202.

To provide some examples of the dedicated portion 202, if during thededicated portion 202, the frequency and phase of the electromagneticwaveform 201 remain substantially constant, a phase comparison betweento RF signals output from the first and second antennas 102-A1, 102-A2may be conducted without the need to condition the RF signals forchanges in frequency or phase, or both, of the electromagnetic waveform201. As another example, modulations in frequency or phase, or both, ofthe electromagnetic waveform 201 may be established before transmissionor may be known by the receiver so that these modulations can beaccounted for in determining the phase difference. Examples ofaccounting for the modulations includes generating an unmodulated formof the RF signals in accordance with one or more embodiments herein, orconfining the sampling periods for determining phase to portions of theRF signals that share one or more common characteristics, e.g., samplingwhile Os are being transmitting and avoiding sampling during transitionsdue to the modulations. In another example, the sampling periods may bedetermined so that RF signals are substantially the same with respect tofrequency and phase, and optionally obtained during different periods oftime.

The timing or one or more characteristics, or a combination thereof, ofthe dedicated portion 202 of the electromagnetic waveform 201 may bedetermined dynamically, e.g., by a transmitter before transmission of amessage packet. The transmitter may be incorporated into thecommunication interface 53 of the device 50.

Additionally, or alternatively, the timing or one or morecharacteristics, or a combination thereof, of the dedicated portion 202of the electromagnetic waveform 201 may be established in accordancewith a communication protocol standard (e.g., WiFi). As an example, thetime position and duration of the dedicated portion 202 of theelectromagnetic waveform 201 may be established for the communicationprotocol so that devices that communicate using this protocol are awarethat the dedicated portion 202 is present in communications, and thatthe dedicated portion 202 may be used as a basis for determining a phasedifference output with respect to waveform output signals that share acommon frequency characteristic. Examples of one or more characteristicsof the dedicated portion 202 that may be determined dynamically orestablished in accordance with a communication protocol standard includea frequency of transmission, a duration of transmission, and a timinglocation within a message packet. For instance, in the illustratedembodiment of FIG. 5, the dedicated portion 202 is provided at the firstfrequency F1 in between modulations representative of symbols such that,during the dedicated portion 202 for phase measurement, a single symbolis repeated (represented by frequency F1, 204).

One or more aspects of the dedicated portion 202 that can be variedbetween message packets 600. For instance, the timing location of thededicated portion 202 in the message packet 600 may be different for onemessage packet versus another message packet. In other words, the timinglocation in one message packet may be different from the timing locationin another packet. This way, the attempts to fake a phase difference(and a resulting angle of arrival determination) can be renderedineffective. For instance, if a bad device attempts to fake a phasedifference, the bad device would need to know the correct location ofthe dedicated portion 202 to generate one or more electromagnetic wavesto fake a phase difference.

The one or more aspects varied for the dedicated portion 202 may becommunicated to the phase detection component 70 to facilitate use ofthe dedicated portion 202 in determining the phase difference. In oneembodiment, the one or more characteristics of the dedicated portion 202to be transmitted in a first message packet 600 are communicated in thefirst message packet 600 but prior to transmission of the dedicatedportion 202 therein. Additionally, or alternatively, the one or moreaspects of the dedicated portion 202 may be communicated to the phasedetection component 70 in an encrypted form. A shared key may beestablished between the phase detection component 70 and the transmitterof the electromagnetic wave 201 to facilitate encryption of theinformation including the one or more aspects of the dedicated portion202 to be communicated to the phase detection component 70.

In one embodiment, the dedicated portion 202 may not have a constantfrequency characteristic. For instance, the dedicated portion 202 mayinclude modulations corresponding to symbols that are defined prior totransmission of the dedicated portion 202. This way, the phase detectormay remove the modulations based on their known values, or sample thededicated portion 202 for one or more periods that substantially excludethe transition periods from one frequency to another. By knowing thetiming of the modulations, the one or more periods may be determined toavoid adverse effects on phase difference measurements due to samplingof the transition periods. The symbols for the dedicated portion 202 maybe communicated in a secure manner to the phase detector beforetransmission, allowing the symbols to be determined dynamically or in amanner that can vary from one message packet to another message packet.

In one embodiment, there may be a plurality of dedicated portions 202dispersed throughout the message packet. The locations of thesededicated portions 202 may remain static or the same in accordance witha standard. Additionally, or alternatively, the locations of thededicated portions 202 can vary from one message packet to anothermessage packet. The locations may be communicated as part of the messagepacket or in a previous message packet, optionally in a secure manner.By varying the locations of the dedicated portions 202, a bad device,which attempts to fake the system into determining an incorrect phasedifference that is beneficial to the bad device, may be renderedineffective.

In the illustrated embodiment of FIGS. 7A-7E, a message packet inaccordance with one embodiment of communications is shown and designated600. The message packet 600 may be defined to include a plurality of bitfields, including a preamble, an address, a payload and a frame sequencecheck. The type and number of bit fields may vary based on thecommunication protocol (e.g., the data link layer of the communicationprotocol). The message packet 600 in the illustrated embodiment may betransmitted as a series of symbols from left to right via theelectromagnetic waveform 201. As discussed herein, the dedicated portion202 or a plurality thereof may be provided in the message packet 600.The location or locations of the dedicated portion 202 and the bitsequence of each dedicated portion 202 may remain static or may bedynamic for a communication session for a transmitter (e.g., theportable device 20) and a receiver (e.g., the antenna array 30 andsensor 40). An example dynamic aspect of the dedicated portion 202include differences in the bit sequence of a dedicated portion 202relative to another dedicated portion 202 (within the same messagepacket or another message packet, or a combination thereof). Anotherexample dynamic aspect of the dedicated portion 202 is the location orlocations of a dedicated portion 202 or a plurality thereof within themessage packet 600 being different from the location or locations of adedicated portion 202 or a plurality thereof within another messagepacket 600. The dynamic aspects of the dedicated portion 202 within amessage packet 600 may be communicated to the phase detection component70 prior to transmission of a message packet 600 or within the messagepacket 600 but prior to occurrence of the dedicated portion 202.

FIGS. 7B-7E depict a dedicated portion 202 of the message packet 600 inaccordance with one or more embodiments of the present disclosure,showing an enlarged view with respect to the dedicated portion 202 inFIG. 7A and showing related aspects of the timing of the message packet600 and the phase detection component 70. The dedicated portion 202 inthe illustrated embodiment is provided in the payload field of themessage packet 600—but the present disclosure is not so limited. Thededicated portion 202 may be provided at one or more other locations ofthe message packet 600.

The illustrated embodiment of FIG. 7B shows that the bit values of thepayload field of the message packet 600 may vary. That is, the portionof the message packet 600 that is identified as the dedicated portion202 may not be the dedicated portion 202 in one message packet 600 butmay be the dedicated portion 202 in another message packet 600.Additionally, or alternatively, the bit values of the dedicated portion202 in one message packet 600 may be different from the bit values ofthe dedicated portion 202 in another message packet 600.

For purposes of discussion, the bit values for a dedicated portion 202in accordance with one embodiment are depicted in FIG. 7C. The dedicatedportion 202 in FIG. 7 includes a repeated sequence 1000, with the 1indicating a start of each sequence.

The phase detection component 70 may determine a phase differencebetween RF signals output from the first and second antennas 102-A1,102-A2 based on samples of the RF signals output from the first andsecond antennas 102-A1, 102-A2 during the dedicated portion 202. The RFsignals output from the first and second antennas 102-A1, 102-A2 may besampled simultaneously or at different times. As an example, if the RFsignals are sampled at different times, the samples may be obtained withrespect to substantially similar sections (e.g., the same type ofmodulation) of the dedicated portion 202-such as the sections identifiedby Os in FIG. 7C. Alternatively, as discussed herein, the samples may beobtained at different times and regardless of any modulations in the RFsignals output (e.g., regardless of whether the sampled sections aredissimilar in the type of modulation) from the first and second antennas102-A1, 102-A2, where the modulations are removed from the RF signals tofacilitate a comparison of phase between the RF signals that isindicative of an angle of arrival.

Sampling of the RF signals output from the first and second antennas atdifferent times may be conducted in accordance with the state of an RFswitch, such as the RF switches 302, 502 described in conjunction withthe illustrated embodiments of FIGS. 6, 8 and 10. The RF switch may beconfigured to pass through the RF signal from one of the plurality ofantennas 102 depending on the state of the RF switch. In the illustratedembodiments of FIGS. 7D and 7E, the RF switch has two states, one inwhich the RF signal from the first antenna 102-A1 is passed, directly orindirectly, to a sampling circuit (e.g., an analog to digitalconverter), and the other in which the RF signal from the second antenna102-A2 is passed, directly or indirectly, to the sampling circuit.

The switching rate of the RF switch may vary depending on theapplication. For instance, in the illustrated embodiment of FIG. 7D, theswitching rate of the RF switch is greater than the bit rate ofcommunications represented in the RF signal. For instance, the RF switchmay be operated with a switching period of 30 ns or approximately 333MHz whereas the bit rate of communications may be approximately 2 Mbps.Alternatively, the switching rate of the RF switch in one embodiment maybe less than the bit rate of communications. An example of this mode ofoperation can be seen in the illustrated embodiment of FIG. 7E in whicheach sampling period spans one or more bits represented in the RFsignal. As another example, both of the switching sections noted as A1and A2 in FIG. 7E may span one sampling period for the second antenna102-A2 and another sampling period for a similar portion of thededicated portion 202 (e.g., the 000 portion of the sequence 1000) maybe conducted for the RF signal output from the first antenna 102-A1.

In one embodiment, the bits or modulations represented in the RF signaloutput from each of the first and second antennas 102-A1, 102-A2 may bedynamically removed from the RF signal so that the phases of unmodulatedforms of the RF signals from the first and second antennas 102-A1,102-A2 may be compared. For instance, phase or frequency modulations inthe RF signal from an antenna 102 may be dynamically detected andremoved from the RF signal, leaving an unmodulated form of the RF signalthat includes phase and frequency information of the RF signal butwithout the phase modulation due to transmission of a symbol.

A. First Embodiment for Phase Detector

A phase detector in accordance with one embodiment of the presentdisclosure is shown in FIG. 6 and generally designated 300. One or moreaspects of the phase detector 300 may be incorporated into the phasedetection component 70. In one embodiment, the phase detector 300 may berealized on a single chip. It is noted that the phase detector 300 andother embodiments of the phase detector may be incorporated as part of areceiver in the object component 50 for demodulating communicationsreceived in the electromagnetic waveform 201.

In the illustrated embodiment, the phase detector 300 may be coupled toan antenna array 30, which may include first and second antennas 102-A1,102-A2 in accordance with one embodiment of the present disclosure. Thephase detector 300 may be a receiver configured to measure the phasedifference between RF signals output from the antennas 102-A1, 102-A2.Antennas 102-A1, 102-A2 may be connected to an RF switch 302, which isconfigured to pass through the RF signal output from one of the antennas102-A1, 102-A2 based on the state of the RF switch 302. The output ofthe RF switch 302 and a local oscillator 305 may be connected to afrequency mixer 304.

The state of the RF switch 302 may be controlled as a function of theswitch input 301, which may be provided by a component of the phasedetector. The switch input 301 may be controlled so that the RF switch302 repeats the sequence of providing an RF output from one of theantennas 102-A1 for a first duration of time and then providing an RFoutput from the other of the antennas 102-A2 for a second duration oftime. The first and second durations of time may be the same, and maycorrespond to the time period of the electromagnetic waveform 201 (e.g.,the reciprocal of the center frequency), or a multiple or fractionthereof (e.g., a harmonic). In one embodiment, the RF switch 302 may beselectively controlled so that the first and second antennas 102-A1,102-A2 are commutated. The switching rate of the RF switch 302 may bedetermined based on the system configuration. The switch input 301 maybe generated by an oscillator.

Although described in conjunction with switching between RF outputsignals of a pair of antennas 102-A1, 102-A2, the RF switch 302 may beconfigured to selectively output an RF output signal from more than twoantennas 102 to an RF output of the RF switch 302. For instance, the RFswitch 302 may commutate among eight antennas 102 disposed in a spacedapart relationship with respect to one another.

In one embodiment the state of the RF switch 302 may selectively changebased on the communication protocol established with the source of theelectromagnetic waveform 201, or based on communications received viathe electromagnetic waveform 201, or a combination thereof. Forinstance, the RF switch 302 may be configured to output an RF outputsignal from the first antenna 102-A1 for a duration corresponding to aplurality of symbols (e.g., 4 symbols) represented in theelectromagnetic waveform 201, and to output an RF output signal from thesecond antenna 102-A2 for a duration corresponding to the same number ofsymbols (e.g., 4 symbols) represented in the electromagnetic waveform201. As another example, the RF switch 302 may be configured to switchbetween the first and second antennas 102-A1, 102-A2 at a ratesubstantially greater than the bit rate or symbol rate of communicationsrepresented in the electromagnetic waveform 201.

In one embodiment, the local oscillator 305 may generate a square wavesignal having a frequency substantially the same as the carrierfrequency or the center frequency of the electromagnetic waveform 201received by the antennas 102-A1, 102-A2. For instance, the frequency ofthe square wave signal may be 2.402 MHz. Alternatively, the output fromthe local oscillator 305 may be a continuous sine wave. In oneembodiment, the local oscillator 305 may be operated at a frequencydifferent from the center frequency or carrier frequency of theelectromagnetic waveform 201. For instance, the frequency of the localoscillator 305 may be higher or lower than the center frequency orcarrier frequency of the electromagnetic waveform 201.

The frequency of the local oscillator 305 may be variable, enabling thephase detector 300 to operate in conjunction with electromagneticwaveforms 201 communicated at different channels or different frequencybands in which communications are transmitted at different centerfrequencies (e.g., a center frequency other than 2.402 MHz).

The RF output from the RF switch 302, which corresponds to the RFsignals from the antennas 102-A1, 102-A2, may be mixed with the localoscillator 305 by the frequency mixer 304. The local oscillator 305 maybe used in conjunction with the frequency mixer 304 to downconvert thewaveform output signal or RF signal output from the antennas 102-A1,102-A2 to an intermediate frequency (IF) signal with a frequencyspectrum having lower frequency content than the center frequency orcarrier frequency. As an example, with a local oscillator 305 operatingat or substantially near the center frequency of the electromagneticwaveform 201, the RF signal from the antennas 102-A1, 102-A2 may beshifted to an IF signal with frequency content substantially centeredabout 0 Hz. An example of the frequency spectrum of such an IF signalgenerally centered about 0 Hz can be seen in FIG. 6, designated as 320.In another example, with the local oscillator 305 operating at afrequency higher than the center frequency of the electromagneticwaveform 201, the RF signal output from the antennas 102-A1, 102-A2 maybe downconverted to an IF signal with a frequency spectrum centeredgenerally about a frequency that is the difference between the centerfrequency and the frequency of the local oscillator 305. In this way,the DC component at 0 Hz can be removed from the signal whilesubstantially preserving the spectral content of the RF signal (e.g.,frequency and phase information). An example of the frequency spectrumof such an IF signal can be seen in FIG. 6, and generally designated330.

With the local oscillator 305, the frequency mixer 304 and the RF signalfrom the antennas 102-A1, 102-A2, the RF signal may be shifted to anIntermediate Frequency (IF) which is a low or zero frequency. The IFsignal can be isolated in the frequency domain by the filter 311. In oneembodiment, the IF signal provided by the frequency mixer 304 may be alow frequency signal, in which case the filter 311 may be a band-passfilter (as shown in FIG. 6) to substantially isolate the IF signal inthe frequency domain. Alternatively, the IF signal provided by thefrequency mixer 304 may be an average of 0 Hz, in which case the signalis considered an analytic signal, having an in-phase andphase-quadrature signal. The filter 311 in this configuration may be alow-pass filter to substantially isolate the IF signal in the frequencydomain.

The signal output from the filter 311 may be provided to phasecomparison circuitry 313, which may include one or more of thefollowing: an analog-to-digital (ADC) filter converter 312, a switch303, first and second digital memories 307, 308 and a phase comparator309. All or some components of the phase comparison circuitry 313 may bedigital and may be configured in accordance with dedicated digitalfunctions or processor-executed code, or a combination thereof.

The analog-to-digital (ADC) filter converter 312 may be configured tosample the signal output from the filter 311 and to preserve thespectral content thereof. The ADC filter converter 312 may be configuredto output digitally encoded values representative of the samplesobtained with respect to the signal output from the filter 311. Thesamples obtained by the ADC filter converter 312 may be digitallyfiltered (e.g., an IIR filter) in the process of generating thedigitally encoded values. The digitally encoded values may be stored inmemory or transferred to a hardware module or a software module, or acombination thereof, that stores the digitally encoded values in memory.

The digitally encoded values output from the ADC filter converter 312may be provided to a switch 303, which may be implemented in hardware orsoftware. The switch 303 may be operated in conjunction with the RFswitch 302 based on the state of the switch input 301. For instance, ifthe state of the switch input 301 corresponds to a first antenna 102-A1,the output of the RF switch 302 may correspond to the RF signal of thefirst antenna 102-A1 and the output of the switch 303 may be associatedwith memory for the first antenna 102-A1. If the state of the switchinput 301 corresponds to a second antenna 102-A2, the output of the RFswitch 302 may correspond to the RF signal of the second antenna 102-A2and the output of the switch 303 may be associated with memory for thefirst antenna 102-A2.

In one embodiment, the ADC filter converter 312 may be provided as ahardware module in an FPGA, and the digitally encoded values of the ADCfilter converter 312 may be directed to different portions of hardwarebased on the state of the switch 303. Alternatively, the switch 303 maybe implemented as part of a software module stored in memory of thephase detection component 70, and configured to receive the digitallyencoded values of the ADC filter converter 312. The switch 303 in thisexample may be configured to direct the digitally encoded values tomemory based on the state of the switch input 301.

As discussed herein, in one embodiment, the RF switch 302 and the switch303 may be controlled in tandem by the switch input 301. The switch 303may provide the IF signal, generated and filtered by the frequency mixer304 and the filter 311, to one of first and second digital memories 307,308. For instance, during the first half of the dedicated portion 202depicted in the illustrated embodiments of FIGS. 2 and 7A, the firstdigital memory 307 may be coupled to store the digitally encoded valuescorresponding to the IF signal. During the second half of the dedicatedportion 202, the second digital memory 308 may be coupled to storedigitally encoded values corresponding to the IF signal. In theillustrated embodiment, because the switch 303 is operated in tandemwith the RF switch 302, 1) the IF signal during the first half of thededicated portion 202 and stored in the first digital memory 307corresponds to the RF signal output from the first antenna 102-A1, and2) the IF signal during the second half of the dedicated portion 202 andstored in the second digital memory 308 corresponds to the RF signaloutput from the second antenna 102-A2.

In one embodiment, after the dedicated portion 202 has elapsed, thedigital memories 307, 308 may be configured to replay or output theirrespective signals by providing them to the phase comparator 309. Thephase comparator 309 may be configured to generate a phase differencebetween the first and second antennas 102-A1, 102-A2 based on the valuesstored in the digital memories 307, 308. The output from the phasecomparator 309 may correspond to the phase difference signal 104 of thephase detection component 70, which is configured according to oneembodiment of the phase detector 300.

B. Second Embodiment for Phase Detector

A phase detector in accordance with one embodiment of the presentdisclosure is shown in FIG. 8 and generally designated 350. One or moreaspects of the phase detector 350 may be incorporated into the phasedetection component 70. In one embodiment, the phase detector 350 may berealized on a single chip. As discussed herein, the phase detector 350may include a secondary receiver configured to generate a secondarywaveform output signal or a secondary RF signal that corresponds to theelectromagnetic waveform 201 received by an antenna 102. The secondaryRF signal may be demodulated to determine the symbols or bitsrepresented in the electromagnetic waveform 201. These symbols or bitsmay be communicated to a primary receiver to facilitate removal of thesymbols or bits from an RF signal, thereby facilitating a comparison ofphase with respect to the electromagnetic waveform 201 received by theprimary receiver. The secondary receiver may share one or more antennas102 of the primary receiver. Alternatively, the secondary receiver maybe coupled to an antenna 102 separate from those coupled to the primaryreceiver, and may communicate the bits determined from the RF signal tothe primary receiver via a separate communications link (e.g., via awireless link separate from the communications represented in theelectromagnetic waveform 201).

The phase detector 350 in the illustrated embodiment is similar to thephase detector 300 in the illustrated embodiment of FIG. 6 but withseveral exceptions. For instance, the phase detector 350 may include oneor more of the following components of the phase detector 300: an RFswitch 302, a frequency mixer 304, a filter 311, an ADC 312, a switch303 and first and second memories 307, 308. The phase detector 350 mayalso include a phase comparator 309 configured to output a phasedifference signal 104 based on a phase comparison of two input signals.

The phase detector 350 in the illustrated embodiment includes primaryreceiver circuitry 352 and a secondary receiver 354 coupled to the firstantenna 102-A1. The secondary receiver 354 may be coupled to a differentantenna 102, as discussed herein. For instance, the secondary receiver354 may be coupled to an antenna 102 that does not provide an RF signalto the primary receiver circuitry 352. More specifically, the secondaryreceiver 354 and an antenna 102 coupled to the secondary receiver 354may be disposed in a separate device (e.g., the primary receivercircuitry 352 may be in one sensor 40 and the secondary receiver 354 maybe in another sensor 40).

The secondary receiver 354 may be configured to demodulate the RF signalobtained from the first antenna 102-A1 to generate a stream ofmodulation information (e.g., a bit stream) representative of themodulations in the RF signal. This modulation information may becommunicated to the primary receiver 352. Communicating the modulationinformation may be achieved via direct electrical connections (e.g., aserial, wired interface) or via wireless communications. In oneembodiment, the modulation information may be communicated from thesecondary receiver 354 to the primary receiver circuitry 352 via awireless communication link that is separate from the communication linkutilized for receipt of the modulation information. The separatecommunication link may be established according to the samecommunication protocol as the communication link used for receipt of themodulation information. For instance, both communication links forreceipt of the modulation information from the electromagnetic waveform201 and transmission of the modulation information from the secondaryreceiver 354 to the primary receiver circuitry 352 may be establishedvia Wi-Fi.

Based on receipt of the modulation information from the secondaryreceiver 354, the primary receiver circuitry 352 may demodulate the RFsignals obtained from the first and second antennas 102-A1, 102-A2. Thedemodulated RF signals may be stored respectively in the first andsecond memories 307, 308 and provided to the phase comparator 309.

Demodulation of the RF signals from the first and second antennas102-A1, 102-A2 may be performed by demodulation circuitry 356 of theprimary receiver circuitry 352. The demodulation circuitry 356 may beconfigured to demodulate the RF signals based on the modulationinformation obtained from the secondary receiver 354. Demodulation maybe conducted in a variety of ways, including via mixing with in-phaseand quadrature phase signals.

C. Third Embodiment for Phase Detector

A phase detector in accordance with one embodiment of the presentdisclosure is shown in FIG. 9 and generally designated 400. One or moreaspects of the phase detector 400 may be incorporated into the phasedetection component 70. In one embodiment, the phase detector 400 may berealized on a single chip.

In the illustrated embodiment, the phase detector 400 may be configuredto measure the phase difference between RF signals output from the firstand second antennas 102-A1, 102-A2. The first and second antennas102-A1, 102-A2 and a local oscillator 403 may be connected respectivelyto first and second frequency mixers 402A, 402B. The first and secondfrequency mixers 402A, 402B may form part of first and second receiversfor receiving communications from the first and second antennas 102-A1,102-A2.

In the illustrated embodiment, the first and second frequency mixers402A, 402B may be configured to shift the RF signal output from thefirst and second antennas 102-A1, 102-A2, respectively, to first andsecond IF signals 403A, 403B. The IF signals 403A, 403B may be low orzero frequency, which can be isolated in the frequency domainrespectively by first and second filters 404A, 404B. The IF signals403A, 403B provided by the first and second mixers 402A, 402B may be alow frequency signal, in which case the first and second filters 404A,404B may be a band-pass filter (as depicted). Alternatively, the IFsignals 403A, 403B may be an average of 0 Hz, in which case the IFsignals 403A, 403B may be considered analytic signals, having anin-phase and phase-quadrature signal.

The output from the first and second filters 404A, 404B may be providedto a phase comparator 406, which in turn provides the phase differencesignal 104 that represents the phase difference between the RF signalsoutput from the first and second antennas 102-A1, 102-A2.

D. Fourth Embodiment for Phase Detector

A phase detector in accordance with one embodiment of the presentdisclosure is shown in FIGS. 10-12 and generally designated 500. One ormore aspects of the phase detector 500 may be incorporated into thephase detection component 70. In one embodiment, the phase detector 500may be realized on a single chip. It is noted that several components ofthe phase detector 500 are described as “blocks” for purposes ofdiscussion-a block may be implemented in software or hardware, or both.One aspects of the block may be implemented in software and anotheraspect of the block may be implemented in hardware.

In one embodiment, the phase detector 500 is configured to detect aphase difference between RF signals output from first and secondantennas 102-A1, 102-A2 irrespective of any modulations in the RFsignals. Any length of data obtained in the RF signals may be analyzedto determine the phase difference. As an example, the phase differencemay be determined without use of a dedicated portion 202 incorporatedinto the message packet 600. In other words, the phase difference may bedetermined with respect to portions of the RF signals output from thefirst and second antennas 102-A1, 102-A2 regardless of whether anymodulations are included in the RF signals during those portions.

In the illustrated embodiment of FIG. 10, the phase detector 500includes several components similar to those described in conjunctionwith the phase detector 300. For instance, the phase detector 500includes: a switch input 501, an RF switch 502, a frequency mixer 504, afilter 506, an ADC 507, and a switch 503 similar respectively to theswitch input 301, the RF switch 302, the frequency mixer 304, the filter311, the ADC 312, and the switch 303 of the phase detector 300. Forinstance, the switch input 501, similar to the switch input 301 maycorrespond to an output of an oscillator as show in the illustratedembodiment of FIG. 10.

The phase detector 500 is different from the phase detector 300 in somerespects. For instance, in contrast to one embodiment of the phasedetector 300, one embodiment of the phase detector 500 may be configuredto determine a phase difference with respect to a pair of RF signalsfrom the first and second antennas 102-A1, 102-A2 regardless of anymodulations in the RF signals or without the need to use a dedicatedportion 202 in the message packet 600, or both.

The phase detector 500 may determine a phase difference of the RFsignals for periods of time substantially longer than a dedicatedportion 202. In one embodiment, the phase difference may be determinedfor a period longer than the message packet 600 or longer than a fieldof the message packet 600. In one embodiment, the phase difference maybe determined continuously with respect to the RF signals output fromthe first and second antennas 102-A1, 102-A2 regardless of anymodulations in the RF signals.

In the illustrated embodiment of FIG. 10, the phase detector 500includes demodulation circuitry 556 configured to demodulate the RFsignals output from the first and second antennas 102-A1, 102-A2. Thedemodulation circuitry 556 may sample portions of the RF signals atdifferent times, and demodulate the sampled portions to yield anunmodulated form of the sampled portions. The unmodulated forms of thesampled portions may facilitate determining a phase difference betweenthe sampled portions of the RF signals irrespective of any modulationsin the sampled portions.

The phase detector 500 of the illustrated embodiment may be configuredto operate as a receiver that measures the phase difference between RFsignals received by the first and second antennas 102-A1, 102-A2. Thefirst and second antennas 102-A1, 102-A2 may receive the electromagneticwaveform 201 and provide an RF signal, also described herein as anoutput waveform signal, representative of the electromagnetic waveform201.

The RF signals provided by the first and second antennas 102-A1, 102-A2may be selected by the RF switch 503 and applied to the mixer 504 alongwith the signal from the local oscillator 505. In accordance with one ormore embodiments described herein, the mixer 504 may shift the RF signalto an Intermediate Frequency (IF) signal, which may be a low or zeroaverage frequency. The IF signal may be substantially isolated in thefrequency domain by the filter 506. As discussed herein, in instanceswhere the IF signal is a low frequency signal, the filter 506 may beconfigured as a band-pass filter. In instances where the IF signal hasan average of approximately 0 Hz, the IF signal may be considered ananalytic signal, having an in-phase and phase-quadrature signal. In theillustrated embodiment, the output from the filter 506 may be digitizedby the ADC 507. Optionally, the filter 506 may be provided after the ADCand filtering may be conducted with respect to the digitized form of theIF signal.

The digitally encoded values output from the ADC 507, which representsamples of the IF signal, may be stored in memory or transferred to ahardware module or software module that stores the digitally encodedvalues in memory or performs an operation on the digitally encodedvalues, or a combination thereof.

In the illustrated embodiment, the digitally encoded values may beprovided to the switch 508, which provides the digitally encoded valuesto either the Digital RF Memory (DRFM) 509 or the direct connectionsignal (or output) 533 depending on the state of the switch input 501.As an example, when the switch input 501 is high, the RF signal from thesecond antenna 102-A2 may be provided from the RF switch 502 and savedin the DRFM 509, and when the switch input 501 is low, the RF signalfrom the first antenna 102-A1 may be provided from the RF switch 502 tothe direct connection signal 533.

The DRFM 509 may be set to record or play-back according to the state535 as applied to the control port 534. For instance, using the examplein the preceding paragraph, when the switch input 501 is low, the storedRF signal from the second antenna 102-A2 may be replayed to the DRFMoutput 538.

The control state or the state of the switch input 501 may commutatewith approximately 50% duty cycle at a rate substantially slower thanthe data rate of the incoming RF signal. The duration of each cycle atthe rate is, for example, at least 10 times as long as each symbolreceived at the first and second antennas 102-A1, 102-A2. The switchinput 501 may control the RF switch 502, the switch 503 as well as theDRFM 509 in tandem. The DRFM 509 may record the applied signal when theswitch 508 applies the signal to the DRFM 509. When the control stateapplies the switch 503 output to direct connection signal 533, the DRFM509 may be in the playback mode.

In the illustrated embodiment, the DRFM output 538 and the directconnection signal 533 are connected to frequency mixers 513 and 514. Thesecond DCO output 536, based on output from a MODULATOR/DEMODULATOR(MODEM) 510, has substantially the same frequency modulation andfrequency to the corresponding DRFM output 538. And, the DCO output 537,based on output from the MODEM 510, may have substantially the samefrequency modulation and frequency to the corresponding directconnection signal 533. As a result, first and second mixers 513 and 514,configured to respectively receive these signals, may produce signalswithout modulation and whose DC amplitude is proportional to the phasedifference of the applied signals. In this way, supplying the second DCOoutput 536 and the DRFM output 538 to the second frequency mixer 514 maygenerate an unmodulated form of the RF signal output from one of theantennas 102-A1, 102-A2. And supplying the first DCO output 537 and thedirect connection signal 533 to the first mixer may generate anunmodulated form of the RF signal output from the other of the antennas102-A1, 102-A2.

The output of the first and second mixers 513, 514 may be low-passfiltered by first and second filters 515, 516 and then provided to thedifference block 517. The difference block 517 may be configured tooutput a DC signal representative of the phase difference of the signalat the first and second antennas 102-A1, 102-A2—i.e., the differenceblock 517 may be configured to output the phase difference signal (oroutput) 104 in accordance with one embodiment of the present disclosure.

The DCO signals 536 and 537 may be generated by applying first andsecond frequency control signals 531, 532 to digitally controlledoscillators (DCOs) 511, 512. The MODEM 510 may receive the unswitchedinput signal 528, the DRFM output signal 538, and the direct connectionsignal 533, and may be configured to generate first and secondmodulation/control signals 531, 532 for the first and second DCOs 511,512. Although the direct connection signal 533 is described generallyherein as being a direct connection with no memory, the presentdisclosure is not so limited. The direct connection signal 533 mayalternatively be based on the switch output signal coupled to the directconnection signal 533 and processed through a software module or ahardware module, or both, before being provided to the first frequencymixer 513 and the MODEM 510. Additionally, or alternatively, the DRFMoutput 538 may be replaced or supplemented with a software module or ahardware module, or both, to generate the signal 538 provided to thesecond frequency mixer 514 and the MODEM 510.

The MODEM 510 in FIG. 10 is shown in additional detail in accordancewith one embodiment in FIG. 11. The MODEM 510, as discussed herein, maygenerate first and second modulation/control signals 531, 532 based onthe unswitched input signal 528, the DRFM output signal 538, and thedirect connection signal 533. The unswitched input signal 528 may beapplied to a Frequency-Locked-Loop (FLL) 525 including a frequencydetector 522, a loop filter 523, and a DCO 524. The DCO 524 may beconfigured to track the average frequency of the unswitched input signal528 with a time constant as set by the loop filter 523 that is longrelative to the switching rate of the switch input 501 (e.g., thecontrol state).

The DRFM output signal 538 and direct connection signal 533 may beapplied to first and second demodulators 518, 519, which may beconfigured to supply binary data respectively to first and secondmodulation filters 520, 521. In the illustrated embodiment, the firstand second modulation filters 520, 521 may filter the signal, receivedrespectively from the first and second demodulators 518, 519, with thesame or similar filtering used in the modulation process applied tosignals received at antennas 102-A1, 102-A2. The signals at the outputof the first and second modulation filters 520, 521 may be summed inblocks 526 and 527 with the DCO frequency control signal 530, therebyyielding the first and second control signals 531, 532.

FIGS. 12 and 13 depict the first and second DCOs 511, 512 in furtherdetail in accordance with one embodiment of the present disclosure. TheDCOs may be synchronous devices whose blocks change state on every clockcycle. In the illustrated embodiment of FIG. 12, the first DCO 511includes an add-accumulate block 544 whose output represents phase. Theoutput of add-accumulate block 544 may be added to itself plus, on everyclock cycle, a phase increment signal, which is the first modulationsignal 532 output from the MODEM 510. The phase increment signal mayrepresent frequency. The phase output from the add-accumulate block 544may be applied to a sine-look-up table 545, which in turn may generate adigital sine wave 537 corresponding to the phase output of theadd-accumulate block 544.

In the illustrated embodiment of FIG. 13, the second DCO 512 may beconfigured similar to the first DCO 511, but with the exception of usinga phase offset 543. The second DCO 512 in the illustrated embodiment maybe an add-accumulate block 541 whose output represents a first phase.The output of the add-accumulate block 541 may be added to itself plus,on every clock cycle, a phase increment signal, which is the secondmodulation signal 531 from the MODEM in the illustrated embodiment. Thephase increment signal may represent frequency. The first phase outputfrom the add-accumulate block 541 may be added to the phase offset 543in an adder block 542 to yield a second phase output. The phase outputfrom add-accumulate is applied to sine-look-up table 540 which in turnsupplies a digital sine wave 536. The second phase output may be appliedto a sine-look-up table 540, which may generate a digital sine wave 536corresponding to the second phase output of the adder block 542.

In one embodiment, the FLL 525 may react slowly to changes in frequencyand even more slowly to changes in phase. As a result, the FLL 525 maynot substantially change phase due to the difference in phase of RFsignals output from the first and second antennas 102-A1, 102-A2 whenthe RF switch 502 is commutated. When multiplying the DRFM output signal538 (or the direct connection signal 533) by a signal with the sameaverage frequency plus frequency modulation as the DRM output signal 538(or the direct connection signal 533) the process may strip off themodulation from the signal and leave a DC signal proportional to thephase difference. The phase offset 543 in DCO 512 may be applied tocompensate for the time delay between sampling the signals at the firstand second antennas 102-A1, 102-A2. As such, there may be a first phasedifference between the second DCO output 536 and the DRFM output 538 anda second phase difference between the direct connection signal 533 andthe first DCO output 537. These first and second phase differences inone embodiment can be readily measured after low pass filtering infilters 515 and 516. Further, the difference between the first andsecond phase difference may arise due to the phase shift at the firstand second antennas 102-A1, 102-A2 so that the final output from thedifference block 517 represents this phase shift.

Directional terms, such as “vertical,” “horizontal,” “top,” “bottom,”“upper,” “lower,” “inner,” “inwardly,” “outer” and “outwardly,” are usedto assist in describing the invention based on the orientation of theembodiments shown in the illustrations. The use of directional termsshould not be interpreted to limit the invention to any specificorientation(s).

The above description is that of current embodiments of the invention.Various alterations and changes can be made without departing from thespirit and broader aspects of the invention as defined in the appendedclaims, which are to be interpreted in accordance with the principles ofpatent law including the doctrine of equivalents. This disclosure ispresented for illustrative purposes and should not be interpreted as anexhaustive description of all embodiments of the invention or to limitthe scope of the claims to the specific elements illustrated ordescribed in connection with these embodiments. For example, and withoutlimitation, any individual element(s) of the described invention may bereplaced by alternative elements that provide substantially similarfunctionality or otherwise provide adequate operation. This includes,for example, presently known alternative elements, such as those thatmight be currently known to one skilled in the art, and alternativeelements that may be developed in the future, such as those that oneskilled in the art might, upon development, recognize as an alternative.Further, the disclosed embodiments include a plurality of features thatare described in concert and that might cooperatively provide acollection of benefits. The present invention is not limited to onlythose embodiments that include all of these features or that provide allof the stated benefits, except to the extent otherwise expressly setforth in the issued claims. Any reference to claim elements in thesingular, for example, using the articles “a,” “an,” “the” or “said,” isnot to be construed as limiting the element to the singular. Anyreference to claim elements as “at least one of X, Y and Z” is meant toinclude any one of X, Y or Z individually, and any combination of X, Yand Z, for example, X, Y, Z; X, Y; X, Z; and Y, Z.

The invention claimed is:
 1. A system for determining an angle ofarrival for modulated communications, said system comprising: a firstantenna capable of wirelessly receiving the modulated communications togenerate a first modulated output; a second antenna separated by adistance from the first antenna, the second antenna capable ofwirelessly receiving the modulated communications to generate a secondmodulated output, wherein the first modulated output and the secondmodulated output are indicative of the modulated communications arrivingat the first and second antennas at different times; wherein themodulated communications includes first and second message packets eachincluding a preamble, a message payload, and a frame sequence check,wherein the first and second message packets respectively include firstand second dedicated portions during which one or more characteristicsof the modulated communications are pre-determined, wherein the firstdedicated portion of the first message packet is provided at a firsttiming location in the message payload of the first message packet,wherein the second dedicated portion of the second message packet isprovided at a second timing location in the message payload of thesecond message packet, wherein the first timing location and the secondtiming location are different such that the first and second dedicatedportions are provided at different timing locations respectively withinthe message payloads of the first and second message packets; and acontroller configured to determine a phase difference between the firstand second modulated outputs received by the first and second antennas,wherein the phase difference is determined based on one or more samplesof the first and second modulated outputs during periods correspondingto the first and second dedicated portions.
 2. The system of claim 1wherein the modulated communications include a plurality of messagepackets, wherein each of the message packets includes a plurality ofdedicated portions.
 3. The system of claim 2 wherein one or more aspectsof the plurality of dedicated portions in the first message packet aredifferent from the one or more aspects of the plurality of the dedicatedportions in the second message packet.
 4. The system of claim 3 whereinthe one or more aspects includes at least one of a) a location of one ormore of the plurality of dedicated portions in the first and secondmessage packet, b) a duration of one or more of the plurality ofdedicated portions in the first and second message packet, and c) atleast one modulation of one or more of the plurality of dedicatedportions in the first and second message packet.
 5. The system of claim3 wherein the one or more aspects of the plurality of the dedicatedportions are communicated in dedicated portion information transmittedvia the modulated communications.
 6. The system of claim 5 wherein thededicated portion information is encrypted.
 7. The system of claim 1wherein the angle of arrival for the modulated communications isdetermined based on the phase difference.
 8. The system of claim 1comprising: a first receiver is coupled to the first antenna to generatethe first modulated output; a second receiver is coupled to the secondantenna to generate the second modulated output; the first and secondmodulated outputs are generated simultaneously by the first and secondreceivers; and the phase difference is determined based on the first andsecond modulated outputs.
 9. A method of determining an angle of arrivalfor modulated communications, the modulated communications includingfirst and second message packets, the first and second message packetsincluding a preamble, a message payload, and a frame sequence check,said method comprising: generating a first modulated output based onwireless receipt of the first message packet and the second messagepacket in a first antenna; generating a second modulated output based onwireless receipt of the first message packet and the second messagepacket in a second antenna, wherein the second antenna is separated by adistance from the first antenna; sampling the first and second modulatedoutputs corresponding to at least a portion of a first dedicated sectionof the first message packet and a second dedicated section of the secondmessage packet, wherein the first dedicated section of the first messagepacket is provided at a first timing location in the message payload ofthe first message packet, wherein the second dedicated section of thesecond message packet is provided at a second timing location in themessage payload of the second message packet, wherein the first timinglocation and the second timing location are different such that thefirst and second dedicated sections are provided at different timinglocations respectively within the message payloads of the first andsecond message packets; and determining a phase difference based onsamples of the first and second modulated outputs.
 10. The method ofclaim 9 comprising determining the angle of arrival based on the phasedifference.
 11. The method of claim 9 wherein each of the first andsecond message packets includes a plurality of dedicated sections. 12.The method of claim 11 wherein one or more aspects of the plurality ofdedicated sections in the first message packet are different from theone or more aspects of the plurality of the dedicated sections in thesecond message packet.
 13. The method of claim 12 wherein the one ormore aspects includes at least one of a) a location of one or more ofthe plurality of dedicated sections in the first and second messagepacket, b) a duration of one or more of the plurality of dedicatedsections in the first and second message packet, and c) at least onemodulation of one or more of the plurality of dedicated sections in thefirst and second message packet.
 14. The method of claim 12 wherein theone or more aspects of the plurality of the dedicated sections arecommunicated in dedicated portion information transmitted via themodulated communications.
 15. The method of claim 14 comprisingdecrypting the dedicated portion information.
 16. A transmission devicefor facilitating determining an angle of arrival for a wirelesscommunication signal transmitted from the transmission device, saidtransmission device comprising: an antenna array configured to transmitthe wireless communication signal via an electromagnetic waveformprovided to remote device; a communication interface including atransmitter configured to transmit a plurality of message packets in thewireless communication signal, the plurality of message packetsincluding a dedicated portion during which one or more characteristicsof the wireless communication signal are pre-determined, whereinpresence of the dedicated portion in the wireless communication signalfacilitates determining an angle of arrival for the wirelesscommunication signal relative to the remote device; wherein thecommunication interface is configured to dynamically vary the one ormore characteristics of the dedicated portion such that the one or morecharacteristics for a first dedicated portion of a first message packetare different form the one or more characteristics for a seconddedicated portion of a second message packet, wherein the one or morecharacteristics includes a location of the first dedicated portion andthe second dedicated portion respectively in the first and secondmessage packet; and wherein the communication interface is configured tocommunicate dedicated portion information pertaining to the one or morecharacteristics to the remote device prior to transmission of thededicated portion.
 17. The transmission device of claim 16 incorporatedinto a system with the remote device, the remote device comprising: afirst antenna capable of wirelessly receiving the wireless communicationsignal to facilitate generation of a first modulated segmentcorresponding to at least a first section of the dedicated portion; asecond antenna separated by a distance from the first antenna, thesecond antenna capable of wirelessly receiving the wirelesscommunication signal to facilitate generation of a second modulatedsegment corresponding to at least a second section of the dedicatedportion, wherein the first modulated segment and the second modulatedsegment arrive at the first and second antennas at different times; anda controller configured to determine a phase difference between thefirst and second modulated segments received by the first and secondantennas.
 18. The transmission device of claim 17 wherein the angle ofarrival for the wireless communication signal is determined based on thephase difference.
 19. The transmission device of claim 17 comprising areceiver operably coupled to the first and second antennas, wherein thereceiver is commutated to generate the first modulated segment and thesecond modulated segment at different time durations.
 20. Thetransmission device of claim 17 wherein the dedicated portioninformation is encrypted prior to transmission via the wirelesscommunication signal, and the remote device is configured to decrypt thededicated portion information.